Transparent quantum dot light-emitting diodes with dielectric/metal/dielectric electrode

Abstract

Quantum dot light emitting diodes (QD-LEDs) are formed that are transparent and emit light from the top and bottom faces. At least one electrode of the QD-LEDs is a dielectric / metal / dielectric layered structure, where the first dielectric comprises metal oxide nanoparticles or polymer-nanoparticle blends and is 10 to 40 nm in thickness, the metal layer is 5 to 25 nm in thickness, and the second dielectric layer is a nanoparticulate, polymer-nanoparticle blend or continuous layer of 30 to 200 nm in thickness and is situated distal to the light emitting layer of the QD-LED.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The present application claims the benefit of of U.S. Provisional Application Ser. No. 61 / 705,676, filed Sep. 26, 2012, which is hereby incorporated by reference herein in its entirety, including any figures, tables, or drawings.[0002]This invention was made with government support under W911NF-07-0545 awarded by the Department of the Army. The government has certain rights in the invention.BACKGROUND OF INVENTION[0003]Light emitting diodes (LEDs) are increasingly used in modern display technologies. LEDs have many advantages over traditional light sources including: low energy consumption, long lifetime, robustness, small size and fast switching. LEDs remain relatively expensive and require precise current and heat management relative to traditional light sources. Fabrication costs are significant and exceed the material costs for some LEDs. Conventional LEDs are made from inorganic compound semiconductors, typically AlGaAs (red), AlGaInP...

AI Technical Summary

Benefits of technology

The invention is about making transparent quantum dot light emitting diodes (QD-LEDs) using quantum dots (QDs) as the light emitting layer, and a special electrode called a dielectric / metal / dielectric (DMD) electrode. This electrode has three layers: a first dielectric layer, a thin continuous metal layer, and a second dielectric layer that is either nanoparticulate or a continuous film. The QDs can be made from a variety of materials and can be doped with rare earth elements or transition metal elements. The DMD electrode is thin and transparent, with low sheet resistance. The invention allows for the fabrication of transparent QD-LEDs that can emit light from both sides.

Problems solved by technology

LEDs remain relatively expensive and require precise current and heat management relative to traditional light sources.

Fabrication costs are significant and exceed the material costs for some LEDs.

Another method is to use a yellow phosphor to convert monochromatic blue light, or two or more phosphors emitting different colors to convert UV light, from a LED to broad-spectrum white light, although color control is limited by this approach.

Organic LEDs (OLEDs) can also be fabricated relatively inexpensively to provide a variety of colors and white light, but OLEDs generally suffer from deficiencies in efficiency and in lifetime relative to inorganic devices as the light-emitting layer, being that of an organic material, typically requires a relatively high current density and driving voltage to achieve high luminance, which promotes degradation of the OLEDs, especially in the presence of oxygen, water and UV photons.

Unfortunately, long term stability is insufficient due to degradation of the organic layer and oxidation of the reactive metal.

Device fabrication requires a costly vacuum deposition method.

For most QD-LEDs, defects can occur at the organic-inorganic interface between the QD-emitting layer and an organic electron transport layer, which lead to poor electron injection into the QD-emitting layer.

However, the charge transporting layers are fabricated through complicated and costly vacuum sputter deposition methods.

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